1. Field of the Invention
This invention relates to a novel device for placement on a computer display screen to determine direction changes for graphics commands. More particularly, it relates to such a device which may be oriented over a graphics symbol on the computer display screen to determine proper orientation and/or translation of the graphics symbol to draw desired patterns on the display screen by means of commands in a graphics language. Most especially, it relates to such a device particularly adapted for use with a computer system running a LOGO graphics language program.
2. Description of the Prior Art
LOGO is a computer graphics programming language that has achieved widespread use, particularly as an educational tool for teaching children and others fundamental principles of computer graphics and geometrical relationships. LOGO utilizes a graphics symbol, called a "turtle", which is oriented and translated on a computer display screen with appropriate commands, to draw patterns on the screen. The turtle is usually represented as a triangular arrowhead. There are two basic commands in the LOGO language: change of direction and change of position. Lateral and angular angular orientation of the turtle on the screen depicts the direction in which a line segment is to be drawn. The turtle is the leading point of any such line segment the computer is instructed to draw.
The orientation of the turtle is measured by the supplements to the inside angles in the desired patterns. For most people, especially children, judging the required laterality and angle for a desired orientation change of the turtle is difficult to do by inspection. Achieving the desired orientation and length of the line segments is usually a trial and error process that makes the use of LOGO commands more difficult than if the laterality, angles and lengths could be better judged.
A wide variety of protractors and similar devices for measuring angles and distances are known in the art. For example, such devices are shown in the following issued U.S. Pat. No. 507,216, issued Oct. 24, 1893 to Colby; U.S. Pat. No. 3,018,552, issued Jan. 30, 1962 to Adams; U.S. Pat. No. 3,203,101, issued Aug. 31, 1965 to Brown; U.S. Pat. No. 3,314,167, issued Apr. 18, 1967 to Allgood; U.S. Pat. No. 3,377,718, issued Apr. 16, 1968 to Savin et al.; U.S. Pat. No. 3,382,591, issued May 14, 1968 to Savin et al.; U.S. Pat. No. 3,492,726, issued Feb. 3, 1970 to Stewart and U.S. Pat. No. 4,057,902, issued Nov. 15, 1977 to Matsui. While the art pertaining to such devices is a well developed one, none of these devices is particularly adapted for use with computer display screens and computer graphics commands.